579 
fxus63 klbf 031955 
afdlbf 


Area forecast discussion 
National Weather Service North Platte NE 
255 PM CDT Thursday Jul 3 2008 


Synopsis... 
500 mb analysis from this morning indicating high pressure anchored 
across the southeastern Continental U.S....extending westward into The Rockies. Two trof's 
noted over Hudson Bay...and off the Washington coast. Another strong 
disturbance was present over southern New England. Surface analysis from 
18z indicating a stationary front extending from the MO 
Ozarks...southwestward into southern OK and the northern Permian Basin of West Texas. High 
pressure is anchored across central and eastern Nebraska with mostly 
clear skies underneath this feature. Moisture return further west 
and southeasterly winds have allowed low level stratus to persist across 
northestern Colorado...as well as the western Panhandle into the early 
afternoon hours. 


Discussion... 


Near term (tonight through Sunday night)...forecasting challenges 
are precipitation chances for Saturday night through Sunday 
night...as well as temperatures and fire potential Saturday night in 
the west. 


Through Friday night...a trough of low pressure aloft will build east 
into western Canada over the next 24 hours...forcing a ridge over the 
central and southern rockies eastward. At the surface...high pressure will 
build east into the Great Lakes and upper Mississippi 
Valley...allowing srly flow and moisture to return to the Central 
Plains on Friday. The return moisture...coupled with afternoon highs 
in the middle to upper 80s will increase sb convective available potential energy to at or near 2000 
j/kg by afternoon...which with upper support would warrant mention of 
thunderstorms. However...upper forcing is dismal tomorrow...and with 
rising 500 mb heights and temperatures tomorrow afternoon...convective 
initiation will be difficult. Low level convergence lacking as well 
tomorrow afternoon...with only marginal moisture convergence noted 
in far southern Nebraska and northern Kansas. 500 mb winds should carry this away from 
western and north central Nebraska. Another location of possible 
initiation is over the Black Hills in the vicinity of a weak 500 mb vorticity 
maximum Friday afternoon. This feature weakens considerably as it moves 
to the southeast Friday afternoon and evening...so not expecting any 
residual convection to make its way into the County Warning Area. 


Saturday through Sunday night...ridging across the Central Plains 
will begin to break down on Saturday as a broad trough of low pressure 
drifts across southern Canada. As the ridge breaks down...very hot air 
will push east of the front ranges of Colorado and Wyoming for 
Saturday. Should see triple digit heat across the eastern Panhandle and 
far southwestern Nebraska as southwesterly flow mixes out the shallow moist 
layer. Further east...deeper moisture will hold temperatures in the lower to 
middle 90s...for locations east of a line from Valentine to North 
Platte. 


As the trough pushes east across the Dakotas and northern Nebraska Saturday 
night...elevated convection over the Panhandle and western 
Dakotas...in the vicinity of the surface trough...will move east into 
better low level moisture becoming scattered across northern Nebraska 
Saturday evening. Have concentrated probability of precipitation in the northern zones as the 
upper level focus remains over the Dakotas and northern Nebraska. 


With respect to fire potential for Saturday afternoon...100+ heat 
looks probable behind the dry line in the Panhandle and far southwestern 
Nebraska as 850 mb temperatures rise into the lower 30s celsius. Though the winds along 
the trough will be marginal...high based thunderstorms capable of dry 
lightning would be enough for a red flag warning. Since this is 48 
hours out....will pass on the information to the oncoming shift and let them 
Ponder over this further. After Saturday night...low precipitation chances 
will continue into Sunday as the upper support for the surface trough 
moves east across the County Warning Area. 


Long term (sunday night through thursday)...main challenge in the 
extended period lies with precipitation chances for Sunday night 
through Monday night. 500 mb pattern...thanks to initial shortwave trough 
Saturday night...will remain zonal Sunday night into Tuesday. An 
embedded shortwave and associated cold front...will move across the 
Central Plains late Sunday night into Monday...spreading thunderstorms and rain showers 
across western and north central Nebraska. Have increased probability of precipitation in 
the northern zones to accommodate better timing and track of best middle 
level forcing. At this time...the Dakotas appear to be the best location for 
precipitation...with Nebraska on the southern periphery of best forcing. 
Best precipitation chances in the southern County Warning Area seem to arrive overnight 
Sunday into Monday...as the cold front slides south into Kansas. At 
this point though upper support seems to be lacking...so will keep 
probability of precipitation generally under 30 percent for now. After Tuesday...the European model (ecmwf) 
and 12z GFS solutions indicating ridging building into the western Continental U.S.. 
increased temperatures into the latter half of next week and go with 
a dry forecast as guidance probability of precipitation remain well below climatology. 


&& 


Aviation... 
axis of high pressure located over the Central Plains will result in 
mainly light/variable winds through Thursday afternoon...with mostly 
clear skies persisting into the evening. Weak isentropic upglide 
develops from kvtn to klbf by 09z in response to a passing upper level 
disturbance moving southeast across the upper MS valley region. The 
ascent associated with the upglide will result in scattered cloudiness at 
10000-15000 feet Friday morning. By 12z Friday...a trough of low 
pressure east of the Front Range is forecast to develop...which will 
cause surface winds to become southerly. 




&& 


Lbf watches/warnings/advisories...none 




$$ 


Aviation...Garner 
short and long term...buttler